title: Outbreak of multidrug-resistant Klebsiella pneumoniae carrying qnrB1 and blaCTX-M15 in a French intensive care unit.
abstract: BACKGROUND
  The prevalence of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae is increasing globally and is a major clinical concern. Between June 2008 and September 2009, 4% of patients in an intensive care unit (ICU) were found to be colonized or infected by strains of Klebsiella pneumoniae multiresistant to ceftazidime, ciprofloxacin, and tobramycin; an investigation was initiated and isolates were characterized by molecular typing and resistance patterns.
  
  
  METHODS
  Antibiotic susceptibilities were determined by Vitek2®, Etest®, and agar dilution. Gene encoding beta-lactamases and plasmid-mediated quinolone resistance PMQR determinants (qnr, aac(6')-Ib) were characterized by PCR, sequencing, and transfer assays. DiversiLab® fingerprints were used to study the relatedness of isolates.
  
  
  RESULTS
  Fourteen isolates co-expressing blaCTX-M15, qnrB1, and aac(6')-Ib-cr were identified. Genotypic analysis of these isolates identified 12 clonally related strains recovered from 10 patients. The increased prevalence of blaCTX-M15-qnrB1-aac(6')-Ib-cr-producing K. pneumoniae coincided with the presence in the ICU of a patient originally from Nigeria. This patient was infected by a strain not clonally related to the others but harbouring qnrB1 and aac(6')-Ib-cr genes, a finding not hitherto observed in France. We suspected transmission of resistance plasmids followed by rapid dissemination of the multiresistant K. pneumoniae clone by cross-transmission.
  
  
  CONCLUSIONS
  This study highlights the importance of microbiological screening for multidrug-resistant strains in ICUs, particularly among patients from regions in which multidrug-resistant bacteria are known to exist.
authors.affiliation: Laboratory of Antibiology, University Hospital of Saint-Etienne, 42055 Saint-Etienne, France. gerald.aubert@chu-st-etienne.fr.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Filippa
authors.forename: Anne
authors.initials: A
authors.lastname: Carricajo
authors.forename: Florence
authors.initials: F
authors.lastname: Grattard
authors.forename: Pascal
authors.initials: P
authors.lastname: Fascia
authors.forename: Faten
authors.initials: F
authors.lastname: El Sayed
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Defilippis
authors.forename: Philippe
authors.initials: P
authors.lastname: Berthelot
authors.forename: Gerald
authors.initials: G
authors.lastname: Aubert